Electrode



-J. D; COBINE May 26, 1953 ELECTRODE.

Filed March 30. 1950 2 Sheets-Sheet l Fig. 1b.-

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ARGON A 0/? HELIUM Invntor:

James D. Cobine, bg

His Attorneg.

J D. COBINE May 26, 1953 ELECTRODE 2 Sheets-Sheet 2 Filed March 30, 1950Fig.7.

POWER SOURCE Inventor: James D. Cobine, y Q 4-71 His Attorney.

Patented May 26 1953 I UNITED STATES PATENT OFFICE 2,640,135 ELECTRODEJames D. Cobine, Schenectady, N. Y., assignor to General ElectricCompany, a corporation of .New York 1 Application March 30, 1950, SerialNo. 152,973

' 12 Claims. (Cl. 219-8) This invention relates to electrodes. Moretrode described herein; Fig. 4 shows the present particularly, itrelates to electrodes used in proelectrode in use as a light source;Figs. 5 and 6 ducing electrical arcs and to the process of makshowseveral configurations of electrode structure ing such electrodes. foruse in light sources; Fig. 7 shows the use of Tungsten fabricated into asuitable form, such 5 the electrode material in a rectifier and Fig. 8as a rod is often employed as an electrode in shows its usein anelectric arc furnace. producing electric arcs for inert arc welding,elec- It has been found that an instant starting and trio arc-furnaces,rectifiers, light sources and the stable arc may be formed by using anelectrode like. In order to produce a stable are, or one comprisingsintered tungsten, thoria and tanwhich will not wander over the arcingend of the 10 talum.

electrode and up its sides, the electrode is oper- More particularly, ithas been found that an ated at such temperature that it is incandescent.instant starting and st are various pp Atthese temperatures, which areat or near the cations may be formed by using an electrode conboilingpoint of the tungsten, the arc current is sisting of tun sten, thor aand tantalum in the supplied mainly by thermionic emission from the 'atO 0f ab O hundred parts y Weight of electrode. The high temperaturesresult in the tungsten to ou five t0 y-fi parts y loss of metal from theelectrode, thus shortening Weight of thoria and about 0.5 to five partsby its life. The necessity for having the electrode w i h f tantalum. Ap f r r e of mat incandescent heat in order to maintain a stablepositions for the present electrode is one hundred are also limits thecurrent which can be used with parts by Weig of tungsten o about five toan electrode of any particular diameter or size. y-five parts by wei ofthoria d One 11 Too large an electrode for a given current will five paby Weight of tantalum e pecific not become incandescent and will,therefore, not preferred composition for the P en electrode is maintaina stable arc. An electrode of too small a one hundred pa s by Weight oftungsten, fi t e a diameter of the current used will evaporate too partsy W i f thoria and three parts of tanrapidly. I talum.

Another disadvantage of tungsten electrodes is In inert gas-Shielded areWelding the use Of the th excessively high current and lt necespresentelectrode results in instant starting of sary to start a stable arc ininert gas-shielded arc the are when a high q cy Spark is pp welding. Forexample, a tungsten electrode or the electrode is touched to the workand withabout 0.10 inch in diameter requires a Starting drawn- The arethus produced is also stable and current of about twenty to thirtyamperes and a Steady, the Cathode pot maining at the arcing p t t of b t190 volts ,-c tip of the electrode and not wanderin up its An object ofthe present invention is to provide sides. The p circuit voltage of t ew ldin an electric arcing electrode which permits instant generator equred for starting an arc with the starting and stable are at lowcurrents. Present preferred electrode is V y be th bject of th presentinvention is to about twenty-four volts D.-C. for an electrode providean electrode which will start instantly at about inch in diemeter- 0nthe other hand, 1 p circuit generator Voltages a tungsten electrode ofthe same diameter re- It is a further object of the invention toproquires an are-Starting Open cu V e Of vide a non-consumable arcingelectrode which about 190 Volts The low Voltage Starting operates attemperatures below the operating characteristic of the present electrodepermits temperature of tungsten alone with substantially the use fsmaller Welding generators than Would n 1 of at g otherwise be required.

It is still a further object of this invention to The instant Startingand stable are teprovide an instant Starting and stable are e1ec nanceof the present electrode produces steady trode comprising sinteredtungsten a w m uniform welds with no irregularities. The action .oobjects W111 become apparent from a of the present electrode is shown inFigs. 1a. and consideration of the following description and The Workpiece is ep e d y l and the the drawingin which Figs. 1a and lb showsche- 5o electrode 2 is held in nozzle 3 and colletu, the matically thetypical action of the welding arc latter bein schematically shown anddepicted in produced with the present electrode; Figs. 2a. and only oneinstance for the purpose of simplifying 2b show'the analogous action ofa plain tungsten t e figure. The are '5 starts instantaneously withelectrode; Fig. shows conventionally an inert the imposition of a highfrequency spark 6 and gas arcwelding'torch insection having the ele'c-'r main st ble. unwavering and unmoving as shown as the electrode ismoved along the work piece I in the direction of the arrow to producethe regular uniform weld shown at l in Fig. 1a. This action,characteristic of inert gas-shielded arc welding with the presentelectrode, is radically opposed to that experienced when using a plaintungsten electrode in automatic welding where the electrode and the workare started moving relative to one another when the high frequencyarc-startin spark is imposed. The typical action of a plain tungstenelectrode is illustrated in Figs. 2a and 2b. Whenthe high frequencyspark t is struck between work piece i and plain tungsten electrode 8held in nozzle 3 and collet 4, the arc does not immediately be comeestablished, resulting in a blank space where no welding occurs onworkpiece l as shown in Fig. 2b. When are 5 is established in steadystate, a good weld results. However, the steady or stable state of thearc {exists only a short time and then the cathode spot and are wanderover the tip of electrode 8 and finally up its sides as shown producingan irregular weld and damaging the nozzle 3 and collet t. The wanderingand wavering arc finally extinguishes, leaving an unwelded region on thework piece until a steady arc has been re-established only to repeatagain its wavering and extinguishing to the detriment of the quality ofthe weld produced on the work piece.

A further disadvantage of the plain tungsten electrode is that the tipbecomes molten and rounded as the cathode spot wanders about its edges.This melting of the electrode tip and the formation of a globule ofmolten metal thereon charges the arc gap distance which may cause thearc to extinguish or produce poor welds. The molten and incandescentcondition of the plain tungsten tip in actual use is also conducive toevaporation of the electrode or even loss of metal by separation ordropping of the moltenglobule from the electrode. On the other hand, thepresent electrode, operating as it does at lower and non-meltingtemperatures, is "sub stantially, if not wholly, non-consumable. The endof the present electrode, being unmelted, will not change its shape asby formation of a molten g-lobule of metal so as to require frequentadjustment of the arc gap distance. .Once the arc gap is fixed, usingthe present electrode, itremains unchanged.

When the present tungsten, thoria and tantalum electrode is used, thedisadvantages of the plain tungsten electrode are obviated. When thetorch is placedin motion with the application of the -high frequencyspark, there is no blank spot in the work 'to be welded because thecathode spot and are are immediately established. Furthermore, onceestablished, the cathode spot and are remain steady at the arcing tip orterminal-of the electrode withno wandering or erratic behavior. The netresult, when using the present electrode, is a steady uniform Weld ofhigh strength which is commenced simultaneously with the imposition ofthe high frequency spark and continues uninterruptedly until the workand torch are deliberately further separated or the current is cut oil".

The advantages of the present electrode are further available whenhand-held welding torches are used. In those cases in which the highfrequency'spark is used to start the oathode spot *and are, theprocedure is much the same as in the use of the automatic machine asdescribed above. When the arc is started by 4 short circuiting the arcgap, employment of an auxiliary carbon starting block or plate isrecommended. In using such a block or plate, it is placed immediatelyadjacent the start of the weld, the electrode being touched to it andwithdrawn to establish the arc, the arc and the torch being then movedover to the work. Such a method avoids contaminating the material to bewelded with the electrode material. Thereafter, if the torch is used byan experienced operator, the only occasion for the extinguishment of thearc is a cutting off of the current when the weld is completed.

As pointed out above, the composition of the present electrodes mayinclude one hundred parts by weight of tungsten, from five to fortyfiveparts by weight of thoria and from 0.5 to five parts by weight oftantalum. Amounts of thoria below five parts by weight in the abovecomposition produce an electrode, the characteristics of which soapproach that of plain tungsten that the advantages described herein arenot attained. Amounts of thoria exceeding forty-five parts by weight inthe above composition tend to cause melting under high currents. In thisconnection, the present electrode is to be distinguished from theso-called thoriated tungsten as known in the illuminating art whichusually contains up to about 1.5 percent of thoria.

The tantalum produces an electrode of such increased strength as to makepractical the use of otherwise fragile electrodes in conventionaltorches which clamp the electrode in place as by means of collets. Aminimum of about 0.5 part by weight of tantalum is indicated to obtainrequisite strength. As the tantalum content of the composition isincreased above five parts by weight, the electrodes tend to crack whenbeing sintered and also 'to adhere to one another when stacked in theheat treating furnace. Vanadium and columbium or niobium may be used inplace of the tantalum but the latter is preferred.

Preferably, the thoria is used in amounts of ten to twenty-five parts byweight for each one hundred parts by weight of tungsten and one to liveparts by weight of tantalum.

The preferred specific composition of the electrode described herein isone hundred parts'by weight of tungsten, fifteen parts by weight ofthoria and three parts by weight of tantalum. Such electrodes startconsistently at an initial open circuit voltage of about twenty-eightvolts which is reduced to about twenty-four volts after arcing for aboutone minute. The voltage is not changed after one hour of arcing at aboutamperes. An electrode of this preferredaspecific composition and of 0.10inchdiameter-will start consistently at ten amperes and --lllS acurrentrange of from about eight to 375 amperes. A plain tungsten electrodeofthe same size has a much more restricted current range of .from about140 to 280 amperes, and requires an .open circuit starting voltage ofabout volts D.-C. forhigh frequency spark starting.

The composition containing five parts by weight of thoria has an'opencircuit starting voltageof forty volts D.-C. for .a-llllo inch -diameterrod, this potential rising toabout .forty-.five voltsafterarcingat 120amperes. 'Thiscomposition constitutes 'the lower 'limit for electrodeswhich are most useful in the present applications. A 0.10 inch diameterelectrode containing ten'par'tsby weight or "thoria requires an opencircuit starting voltage of twenty-five volts D.-C. which increased tothirty volts after arcing at 200 amperes. Larger amounts of thoria thanthe fifteen parts by weight per one hundred parts by weight of tungstenappear to offer no advantage. While, as pointed out above, the electrodecontaining fifteen parts by weight of thoria has an open circuitstarting voltage of twenty-eight volts which reduces to twenty-fourvolts, twenty-five parts by weight of thoria, gives an open circuitstarting voltage of about 22.5 volts D.-C. However, the slight decreasein starting voltage of about one and one-half volts does not warrant theaddition of the larger amount of thoria, especially since the arc startsor stabilizes no better than with the fifteen parts by weight of thoria.

The sintered tungsten-thoria-tantalum electrode may be fabricated in anyof a number of ways which will occur to those skilled in the art. Atypical manner of preparing the present electrodes is as follows:

Powdered tungsten, thoria and tantalum are ball-milled in the dry stateuntil throughly mixed; usually several hours is sufficient. To producean electrode having the preferred composition, for example, the mixturewould consist of 100 parts by weight of tungsten, fifteen parts byweight of thoria and three parts by weight of tantalum. For practicalpurposes it is preferable to use in lieu of tantalum metal, a tantalumcompound such as tantalum hydride, carbonate, oxide and the like toprovide the required amount of tantalum.

The above mixture may be pressed dry in suitable molds under a pressureof about 5000 pounds per square inch to produce dense, void-free rodswhich are ready for firing or sintering. The sintering process should becarried out preferably in a reducing or non-oxidizing atmosphere such asthat which is afiorded by hydrogen. The temperature of the furnaceshould reach a temperature of the order of 2000 C. A suitable sinteringprocedure is to place the rods in a hydrogen atmosphere furnace at roomtemperature and gradually and uniformly raise the temperature to about1950 C. over a period of about five hours, holding the temperatureconstant at 1950 C. for about thirty, minutes and cooling gradually toroom temperature with the furnace shut oil. The sintered rods may, ifdesired, be heated to about 2100 C. to 2400 C. for five to ten minutesin an argon atmosphere or in a vacuum to remove absorbed hydrogen. Thistreatment reduces the electrical resistivity and increases the strengthof the rods. For the present welding electrodes an equivalent eflect isproduced when an arc is first drawn so that the heat treatment in vacuumor argon is not essential so long as care is taken in handling theelectrodes prior to arcing. However, the above argon or vacuum treatmentis recommended when the rods are to be stored or handled to any extent.

While a specific time-temperature sintering treatment has been describedabove, it will be readily appreciated by those skilled in the art thatshorter or longer times of treatment may be used depending on thetemperature used. With higher temperatures, a shorter period may be usedwhile at lower temperatures the treatment should be longer.

Alternatively, the present electrodes may be produced by the extrusionprocess. In this case thereshould be mixed with the dry constituentmaterials a paste material such as of sugar syrup or tragacanth or flourand water which will produce an extrudable mass and which will burn offor be otherwise removed during firing or sintering. An example of such abinder is a paste made from ordinary cereal flour of suflicientconsistency to bond the electrode material prior to sintering. Asuitable paste or binder may be made by cooking about ten parts byweight of wheat flour in one hundred parts by weight of water at C.until the mixture is translucent. The binder may then be mixedthoroughly with the dry electrode materials in an amount to give properextruding through regular dies. The extruded, raw rods are then driedand sintered as above.

In operation, the improved electrode of this invention may be used inany conventional inert gas-shielded arc welding apparatus, a typicalform of which is illustrated in Fig. 3. As shown, the present electrode2 is held in a spring collet 9 which in turn is attached to tube II)which is preferably of copper. Electrode 2 may extend into tube II)which serves as a means for supplying inert gas, such as argon orhelium, about the electrode and also serves as a conductor for carryingthe welding current to electrode 2 through collet 9. Tube I0 issurrounded by an electrically insulating sleeve II which, in turn, issurrounded by a protecting casing I2 of some durable material such asiron or steel. Nozzle i3 is frictionally engaged with one end of casing12 and provides a chamber-enclosing the end of tube l0 and collet 9mounted thereon. Shielding gas supplied through tube 10 flows into theabove chamber through a plurality of holes M in the side walls of tubeI0 and is discharged from nozzle l3 about the arcing terminal ofelectrode 2. One terminal of a source of arc welding current isconnected by conductor l5 to tube l0 and the other terminal is connectedby conductor IE to a work-supporting table II. Parts l8 to be welded aresupported on table H with their edges adjoining lengthwise.

The advantages attained by the use of the present electrode do notdepend upon any socalled fluxing action, the electrode material notentering the weld or forming a sheath over it. The only blanketingphenomenon present in welding according to this invention is that of theinert gases fed through the welding torch nozzlewhich shield theelectrode and the molten part of the weld metal. There is nocontamination of the weld or welded parts by any extraneous material andparts so welded are immediately available for further use withoutcleaning.

The use of the present non-consumable electrode enables the cathode spotand are in inert gas-shielded arc welding to become immediately andpermanently established on the tip of the tungsten electrode with nowandering or wavering of the cathode spot and are up the sides of theelectrode or onto other metallic parts of the welding torch or fixture.Once established the only occasion for extinguishing of the arc isdeliberately and excessively increasing the arc gap distance or cutting01f the current. The electrode of this invention is also unique in thatthere is provided a mechanically strong electrode which in integral formprovides a stable steady are without the use of coatings and the like onthe electrode or material to be welded which is easily displaced.

Electrodes of the present composition have also been found very-usefulaslight sources. 'In this connection it maybeusect any the usual atmqspheres such as. of mm'cncyv vapor' and of the so-called inert gasesand also. nitrogen, cam-hon ioxide and hydrogen among others. In suchuse aconventional. tube structure, such as that shown in. Fig... 4, maybe: used. In. the figure the aloetrodes; of. the-.- presentinvention l9:and 2c are-fixed 1. support rods 2% and 22' respectively which in turn.are fixed,- to. contact. members 23 and 24'. Contact members. 23: and 24pass. through the stem. press; 25; and base 2'6. of the lamp which areenclosed in glass. envelope 2 12 filled with gas 2i}. When. the lamp.is. operated under A.-C. current it is. preferred to use elcctnodeelements, such as are. shown more. clearly in Fig. 5, whereintheelectrode I9 or 20 consists" of a, recessed tungsten holder 29.containing a mass of the present sin.- tered electrode material whichis. inserted therein. It is preferable to recess the material 3:0"slightly within holder 29: as shownwhen op-- erated under Aim-C. currentto prevent damage to the electrode material during' the hal -i cyclewhen the electrode serves asanode.

When the lamp is operated under Dt-(C. it ispreferred to use dissimi-lanelectrodes, thepresent material being used as cathode with plaintungsten usedas anode. This arrangement is illus trated in Fig. 6wherein the anode 3+ is ofplain tungsten. The cathode 32- consists of aholder 33 of tungsten in which has been inserted a mass 34 of thepresent tungsten-thoria-tantalummaterial.

The above are lamp operates very; satisfactorily under a startingvoltage ts twenty-five volts 11-6. and tent amperes using electrodematerial 0 .125 inch. in diameten Such a lamp having an argonfil lingatatmospheric pressure gives a light output of 59 ,000 lumensat 200amperes at efiiciency of about lumensper'watt. The light from the arcissteady in characterwith noflickering, the cathode spot and are remainingfixed at one place at the arcing tipof the electrode. Arclamps using thepresent electrode may also be used as flashlamps: and such roleshow verylong life withno fluttering on flickering of the are light source. V

The present electrode material also be used to advantage the so-calledcold cathode rectifier shown-in 7. In the sealed glass onvelope 35,filled with an inert gas 3% such as argon, is mounted an anode 31 on asuitable con-- ducting support 38. Preferably the anode i soigraphite orsimilar material and has a relative lylarge circular surface. Thecathode 38 of the present sintered tungsten-thotia.-tantalum is insertedin a. suitable holder 4!! such as a tungsten rod. Using a cathode 39about one-sixteenth inch in diameter and an an de about oneand one halfinches in diameter the rectifier has a: r e n f the r e of; one undredaniperes.

The. electrodes. of. this. invention may also be used with excellentresults in. lectric. arc. tor-- naces in which the arcing electrode is,used. the. cathode and the. melt or material to, be, melted as theanode. furnaceis, shown in Fig. 8 wherein. the fiurnace. 41,

is. shown. in. cross section. with the. present. elect-.1

trade. 42. projecting through. the ten. of: the. tun-- nace to. withinarcing, distance of melt, 4,3,. The t d nd. me t. 3-. co nected. thncughconductors. M and 45 respectively. to, power;- source 4.6 The, use, of.the. meson-t.- electrode in such furnace. obviates, the wandering, atthe a naneement DfiSHQh .11

8 cathode spot and arc up' the sides'oiithe'electrode. provides. asteady arc of maximum efficiency and prevents. accidental over-extensionand extingui'shment of; the are.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A sintered, non-consumable, inert gas shielded arc welding electrodewhich is capable of starting an are instantly and maintaining a stableare at temperatures below its incandescent temperature, said electrodecomprising, by weight, one hundred parts of tungsten, from five toforty-five parts of thoria and from one-half to. five parts of a metalchosen from the group consisting of tantalum, vanadium, and niobium.

2-. A sintered non-consumable electrode comprising by weight onehundred: parts of tungsten, five to forty-five parts of thori-a andone-half to five parts ofa metal chosen from the group consi'sting: oftantalum, vanadium and niobium.

3'. A non-consumable electrode which is. ca pable of starting an areinstantly and maintaining a. stablearc, said electrode comprising onehundredp-arts by weight of tungsten, from about five to forty-five partsby weight of thoria. andfrom about one-half to fiveparts by weight oftantalum.

4. A non-consumable electrode which is ca cable of starting an instantlyand maintain-- ing a stable are, said electrode comprising by weight onehundred parts of tungsten, from about five to twenty-five parts ofthoria and one to fiveparts of tantalum.

5. An electrode which is capable-of: starting an are instantly andmaintaining a stable are, said electrode comprising by weight about onehundred parts of tungsten, about fifteenparts of thoria and aboutthree-partsof tantalum.

6. An electrode which has instant starting and stable are operatingcharacteristics when energized by welding circuits providing opencircuit voltages as low as about twenty five volts 11-0., said electrodecomprising by weight about one hundred parts of tungsten, about five tofortyfive parts of thoria and about onetofive parts of tantalum.

'7'. In are lighting apparatus, a. sinteredelsetrode comprising, byweight, one hundred parts oftungsten, from five to forty-frveparts ofthoria and from one-half to five parts of a metal chosen from the groupconsisting of tantalum, vatna diuni, and niobium.

8'. In rectifier apparatus, a sintered electrode comprising, by weight,one hundred partsof tungsten, from five to forty-five parts of' thori'aand f roin one-half to five parts of a metal chosen from the groupconsisting of tantalum, vanadium, and niobium.

9.. In. an. electric arc furnace, a sintered electrode comprising, byweight, one hundred. parts.

oi tungsten, five to forty-five parts. of thoria, and.

from one-ha1f to. five parts of a. metal. chosen. from the groupconsisting of tantalum, V3115? dium, and niobium.

10*. In inert gas shielded are welding. apparatus; a sinteredlelectrodecomprising, by weight, one hundred parts of tungsten, from five tofortyfive'parts of thoria and fromv one-half to five parts, by Weight,of a metal selected from the group consisting oi. tantalum, vanadium,and niobium.

l1. sintered non-consumable electr'od'e which is; capable of startinga-narc instantly and maintaining; a stable are, said electrodecomprising a one hundred parts by weight of tungsten and five toforty-five parts by weight of thoria.

12. A sintered non-consumable electrode which is capable of starting anare instantly and maintaining a stable arc, said electrode comprisingone hundred parts by weight of tungsten and lit-- teen partsby weight ofthoria.

JAMES D. COBINE.

References Cited in the file of this patent UNITED STATES PATENTS NumberNumber Number 10 8,421 20,227

Name Date Palmer July 11, 1933 Taylor Oct. 16, 1934 Pavlecka Mar. 23,194; Labosco June 21, 1949 Lancaster et a1 July 18, 1950 FOREIGN PATENTSCountry Date Great Britain 1908 Great Britain 1907

